Nuclear reactors emit an elementary particle known as an antineutrino due to nuclear fission. An antineutrino is an anti-particle of another elementary particle known as a neutrino. The antineutrinos emitted from a reactor core carry information about the fission reactions. For instance, the fissile content of reactor cores can be estimated by monitoring the emission rate and energy spectrum of the emitted antineutrinos. Thus, antineutrinos have become an important source of information for fundamental physics research and for the nuclear non-proliferation community.